University Researchers Develop Switch That Uses A Single Electron

A finding published in the journal Nature Nanotechnology shows researchers developing a switch that can be altered in a targeted manner by using a single electron. The group of international researchers is from Tu Wien, IBM Zurich, the University of Zurich, and the University of Vienna.

Scientists understand that almost all electronics require transistors to function optimally, because computer chips require transistors to operate as logic circuits. Most transistors are composed of silicon crystals mixed with several atom types; but the research team made a transistor that is make up of a single molecule and functions differently from others.

Known as a switch molecule or nanoswitch, this new transistor uses two electrodes instead of the three normally used by most transistors.

Robert Stadler of the Institute of Theoretical Physics at TU Wien noted that the ability to take on two different states is what sets transistors apart; and any of these two states determines the capability of current to enter or barred. Normal transistors are made up of silicon crystals with three contacts – one of them supplies the current and the other takes on the flow, depending on the voltage applied at the third contact.

Older transistors used to be bulky and occupy larger spaces in electronics, but these have been reduced in size and made more compact in today’s electronics, serving to improve efficiency.

"With extremely small crystals you no longer have sufficient control over the electronic properties, particularly if only a small number of dopants remains and the gate's insulating layer allows increasingly more leakage," Stadler explained. "However, if you switch from crystals to organic molecules at the nanoscale, you then have new opportunities to change the transport characteristics."

The researchers eventually synthesized organometallic molecular materials composed of different atoms of molybdenum, iron, and ruthenium. These are about 2 ½ nanometers long, and they are connected with two gold contacts before voltage is allowed to flow into them.

"Directly on the molybdenum atom there is a certain space which can be occupied by an electron," Robert Stadler said. "The amount of current that can flow through the molecule at a certain voltage depends on whether or not there is actually an electron occupying this space or not."

Individual teams making up the research project were separately funded by the Austrian Science Fund, Society of Austrian Chemists, Austrian Academy of Sciences, Springer Verlag, and the Swiss National Science Foundation.